Hardware-In-the-Loop (HIL) is increasingly recognized as an effective approach for simplifying the process of prototyping and testing of complex systems. In the HIL approach, real hardware components being tested interact with an operational virtual environment that combines a real-time simulation engine with an electronic interface for analog and digital signals. Subsystems signally coupled with the hardware are replaced and emulated by virtual models reproducing both the dynamic behavior and the signal interactions of their real counterparts. The dynamic behavior is predicted executing a real-time simulation of mathematical models of the subsystems; each digital and analog signal necessary for the normal operations is replicated by means of an electronic interface. In a realistic HIL experiment, the hardware under test cannot distinguish the real environment from its emulated equivalent. As an example, parts of a vehicle (e.g. electronic boards, sensors) can be tested under different operating conditions with a simulated model of the vehicle where they will be installed. At present, HIL techniques are commonly adopted in many fields of research and industry (e.g. automotive, avionics, electronics) and it has been demonstrated that they can drastically reduce time and costs in the design and testing process. Different platforms for HIL simulation have already been developed and are currently commercially available, such as Opal-RT, dSPACE, RTDS. However, HIL techniques are mainly confined to testing the low-power section (i.e. electronic boards, sensors, low-power actuators) of complex systems since only a signal coupling between the real hardware and the HIL platform is provided.
A natural extension of the concepts of HIL leads to Power-Hardware-In-the-Loop (PHIL) simulations in which natural couplings (nodes involving conservation of energy) are established and a much more significant amount of energy can be virtually exchanged between the simulated environment and the hardware being tested. Practically speaking, a PHIL platform is an extension of a HIL platform where a high performance power amplifier is used as interface between the real and the simulated world. The main challenge is to realize this addition with null or at least minimum impact on the overall platform performance. This means that the control system of the power amplifier must present a bandwidth significantly higher than the range of frequencies under analysis within the experiment. A PHIL platform that can be utilized to emulate the behavior of an electrical machine in order to perform verification tests on power electronic converters is needed.